This invention relates to a switch operating mechanism.
Application of coil springs to spring type operating mechanisms for circuit breakers have been disclosed by Japanese Patent Application (OPI) No. 96619/1986 (the term "OPI" as used herein means an "Unexamined published application"), Japanese Patent Application Publication No. 17449/1980, and Japanese Utility Model Application (OPI) No. 9142/1985.
One example of a conventional spring type operating mechanism is as shown in FIG. 6.
In FIG. 6, a housing 1 includes a a cam shaft 2 supported on the housing. A cam 3 is mounted on the cam shaft 2. A ratchet wheel 4 is mounted on the cam shaft 2. A making spring 5 is provided for generating torque to turn the cam shaft 2 clockwise. A lever 6 is rotatably supported on the housing 1 through a shaft 7, the lever 6 having a pin 8 and a roller 9. A breaking spring 10 is coupled to the lever 6 (being compressed in the case of FIG. 6). A pawl shaft 11 is coupled through a gear (not shown) to an electric motor (not shown). When the making spring 5 is at the deenergization position, the motor (not shown) is rotated to permit the eccentric motion of the pawl shaft 11.
Further in FIG. 6, reference numeral 12 designates pawls mounted on the pawl shaft 11, which rock as the pawl shaft 11 rotates. A pin 13 is provided on the ratchet wheel 4 and making latch 14 is engaged with the pin 13. A making trigger 15 is engaged with the making latch 14. A making electromagnet 16 is provided having a plunger 17. A tripping latch 18 is engaged with the pin 8. A tripping trigger 19 is engaged with the tripping latch 18. A tripping electromagnet 20 with a plunger 21 is provided. The movable contactor 22 of the circuit breaker is coupled through a link mechanism 23 to the lever 6.
The circuit opening operation of the spring type operation mechanism thus constructed will be described.
In FIG. 6, the lever 6 is biased in the clockwise direction by means of the breaking spring 10, but it is held by the tripping latch 18 and the tripping trigger 19. Therefore, when, under this condition, the tripping electromagnet 20 is energized to turn the tripping trigger 19 counterclockwise, then the tripping latch 18 is disengaged from the pin 8, as a result of which the lever 6 is turned clockwise, and the movable contactor 22 is moved to open the circuit with the aid of the link mechanism 23, as shown in FIG. 7.
Now, the circuit closing operation will be described. In FIG. 7, torque is applied to the cam shaft 2 by the making spring 5 coupled to the ratchet wheel 4 so that the cam shaft 2 is turned clockwise, and the torque is maintained by the making latch 14 and the making trigger 15. Therefore, when, under this condition, the making electromagnet is energized to turn the making trigger 15 counterclockwise, the latch 14 is disengaged from the pin 13 of the ratchet wheel 4, as a result of which the cam 3, which is fixedly mounted on the cam shaft 2, is turned clockwise while the lever 6 is turned counterclockwise while compressing the breaking spring 10. FIG. 8 shows a state of the spring type operating mechanism in which the circuit closing operation has been accomplished and the pin 8 is held by the tripping latch 18.
The making spring is energized as follows: As shown in FIG. 8, when the circuit closing operation has ended, the making spring 5 is in a deenergized condition. The pawl shaft 11 is coupled through the gear (not shown) to the motor (not shown), and when the making spring 5 is in the deenergized condition, the motor is started to turn the pawl shaft 11. In this operation, since the pawl shaft 11 is eccentric, the two pawls 12 mounted on the pawl shaft 11 rock. By this rocking operation, the ratchet wheel 4 is turned clockwise to energize the making spring 5. At a position over the dead point, clockwise torque is applied to the cam shaft 2, and the making latch 14 is engaged with the pin 13 as shown in FIG. 6. Under this condition, the pawls are confronted with the part of the ratchet wheel 4 which has no teeth, and therefore even if the pawls 12 rock, no torque is applied to the ratchet wheel 4, and the pawl shaft 11 is not turned, so that the rotation of the motor gives no overload to the pawls 12 or the making latch 14.
As is apparent from the above description, in the conventional switch operating mechanism thus constructed, the elastic force, in the linear direction, of the compressed coil spring is converted into torque with the aid of the lever. Therefore, the switch operating mechanism suffers from a problem in that it is difficult to operate the movable contactor at high speed.